Is the Lorentz signature of the metric of spacetime electromagnetic in origin?

We formulate a premetric version of classical electrodynamics in terms of the excitation H = (H, D) and the field strength F = (E, B). A local, linear, and symmetric spacetime relation between H and F is assumed. It yields, if electric/magnetic reciprocity is postulated, a Lorentzian metric of spacetime thereby excluding Euclidean signature (which is, nevertheless, discussed in some detail). Moreover. we determine the Dufay law (repulsion of like charges and attraction of opposite ones), the Lenz rule (the relative sign in Faraday's law), and the sign of the electromagnetic energy. In this way, we get a systematic understanding of the sign rules and the sign conventions in electrodynamics. The question in the title of the paper is answered affirmatively. (C) 2004 Elsevier Inc. All rights reserved.